Method of and apparatus for controlling the combustion of oil in oil burners



y 1, 1930. B. GREENFIELD 1,768,901

METHOD OF AND APPARATUS FOR CONTROLLING THE COMBUSTION OF OIL IN OILBURNERS Filed July 12, 1921 2 Sheets-Sheet 1 July 1, 1930. B. GREENFIELDMETHOD OF AND APPARATUS FOR CONTROLLING THE COMBUSTION OF OIL IN OILBURNERS Filed July 12, 1921 V 2 Sheets-Sheet 2 l I l 1 1 i w llll II Ill32 W mum/l WMM M oil in oil burners.

Patented July 1, 1930 unite; rnrss ,P-ATSEN o'FFicE BENJAMIN GREENFIELD,F BARTL'ESVILLE, OKLAHOMA, ASSIGNOR TO DOHER-TY RESEARCH COMPANY, OF NEWYORK, N. Y., A. CORPORATION OF DELAWARE METHOD OF AND APPARATUS FORCONTROLLING THE COMBUSTION OF OIL IN OIL BURNERS Application filed Ju1y12, 1921. Serial No. 484,141.

This invention relates vto a method and apparatus for controlling thecombustion of The invention will be hereinafter described, by Way ofexample, as applied to a field boiler of thetype for drilling oil wells,

In the use of oil burnerslfor commercial purposes, as for example, inboilers, it is customary to maintain from to 60 pounds pressure persquareinch on'the oil burner header and to vary the rate of feed of theoil to the burner by adjustment of the burner regulating valve.

Gil feeding systems have, however, been devised in which the regulationof the feed of the oil is obtained by varying the pressure of the oil atthe oil burner header from about 30 pounds to about 60 pounds per squareinch. In certain of the last-mentioned systems thevariations in thepressure of the oil and, consequently, in the rate of feed of the oil,are'accomplished automatically. In both the hand-controlled andautomatic systems in which the rate of feed of the oil is regulated bychanging the pressure on the oil, a control valve is usually provided.at each oil burner for manually modifying the pressure regulation. Ihepressure of oil as it issues from a burner is, of course, the same asthat surrounding the burner, and the pressure prevailing about a burneris ordinarily atmospheric or. slightly below atmospheric. The drop inpressure due to oil passing through the oil burner itself is usuallyvery small. The greater part of the drop in pressure fromanamountvarying between 30 and'GOpounds to atmospheric is eifected atthe regulating valve. I

As a consequence of the high pressure on the oil at the regulatingvalves of oil burners, the valve openings under normal conditions ofoperational-e small. Even in the case of a burner of large capacity inwhichthereg: ulating valve presents a relatively large openwhen theburner is being operated atits maximum rate, the opening becomes smallat the lower rates of combustion asthe fire is turned down. reason ofthe small size'of its opening, the burner regulating valve obstructs themovement throughkit ofthe foreign solid matter usually present in fueloil, wlth the result that such matter accumulates on the supply side ofthe valve and seriously relatively low rates of flow is elongated andnarrowas in the case of the usual globe valve or needle valve. In thisposition of adjust ment the valve acts as a strainer, stopping allforeign matter that cannot pass through the narrow slit.

Inasmuch as the rate of flow of oil through I an opening carriesdirectly as its area and the area of the opening varies substantially asthe square of what may be denominated its mean dimension, assuming thatthe length and breadth of the area are simultaneously increased ordecreased, it follows that valves presenting small openings are verysensitive, it being understood that an equal change in its meandimension will produce a much larger change in the area of a smallopening than in that of a relatively large one. Accordingly, in the useof the present systems of feeding oil, a minute adjustment of theregulating valve produces a large change in the rate of flow of oiltothe burner. On this account it frequently happens in the use ofoil-fired boilers that a small opening movement of the valve passes toomuch oil to the boiler and causes the stack of the boiler to smoke, andwhen the valve is turned toward closed position the flow of oil .is shutoff so to boilers is that when a correct adjustment is finally obtainedit will continue for av short interval only. During. this interval solidmatter may accumulate at the valve and reduce the flow, or matter heldback by the valve, during the adjustment =may work through the valveopening and allow an excess of oil to flow to the boiler.

A further disadvantage of oil feeding systems as at present constructedis that by their use an operator can obtain almost unlimited combustioncapacities with resultant dam age to the heating appliance or to theprocess in which the heating appliance is being used. This source oftrouble is aggravated by the necessity of making frequent adjustments ofthe regulating valve and the inability of the operator to determine theactual rate of oil flow.

A still further disadvantage in the useof present oil feeding systems isthat since the actual rate of flow of oil to the oil burner can not beaccurately controlled, it is impossible to regulate the *entilation ofthe burner so as to provide the amount of air needed for completecombustion of the (Hi without supplying a large excess of air.

It is an object of this invention to feed oil to a burner at a ratewhich can be readily and accurately determined and regulated.

A further object of the invention is to feed oil to a burner in a mannerwhich will enable a desired rate of feed of the oil when onceestablished to be retained unchanged without adj ustment of theflew-regulating means.

A still further object of the invention is to control the ventilation ofan oil burner so that at all rates of feed of oil, the amount of airadmitted to the burner will be suflicient for complete combustion of theoil but will not be in any considerable excess over the amountrequiredfor complete combustion.

In the fulfillment of these objects in accordance with the invention,the flow of oil to the burner is controlled by a low pressure drop ordifferential across an orifice, and the rate of flow of oil to theburner is regulated by varying the pressure drop across the orificebetween zero and a desired maximum. The pressure drop across the orificein most installations is, preferably, limited to an amount notsubstantially exceeding one pound per square inch, and the orifice ismade of relatively large size so that all foreign solid matter usuallyto be found in fuel oil may pass through it without obstruction.Preferably, the orifice is circular and the part which contains theorifice is so formed that the size of the orifice cannot be changedwithout substitution of parts, thereby obviating all danger of the sizeof the orifice being unduly restricted or increased by the operator.

In accordance with a further feature of the invention, the differentialpressure across the orifice is controlled through the agency of agaseous fluid, and the feeding of the oil is, preferably, accomplishedin such a way that oil is fed to the burner only when there is a greatergaseous fluid pressure on the supply side of the orifice than on itsdelivery side. Obv1ously,var1ous gaseous fluids may be used withoutdeparting from the principles of the invention, but when the inventionis applied to steam boilers, it is preferable, for the sake ofconvenience, to utilize steam withdrawn from the boiler.

A further feature of the invention resides in simultaneously varying therate of feed of oil to the burner and regulating the ventilation of theburner so that the amount of air admitted to the burner is alwayssubstantially that required for complete combustion of the oil. Variousother features of the invention pertain to the utilization of steam orother gaseous fluid for varying and limiting the rate of feed of theoil, atomizing the oil, regulating the ventilation of theburner, andreducing the feed of oil to a boiler when the pressure of the steam inthe boiler tends to exceed a pro-determined degree.

Still other objects and features of the invention will appear as thedescription proceeds and will be pointed out in the appended claims.

In the drawings which show a preferred embodiment of the invention:

Fig. 1 is a view in side elevation of an oil- [ired boiler equipped withcombustion controlling apparatus illustrative of the invention.

Fig. 2 is a view of the boiler in end elevation looking from the rightin Fig. 1.

Fig. 3 is a sectional View in elevation of the device for regulating thefeed of the oil.

F ig. 4 is a detail view of the orifice chamber.

Fig. 5 is a sectional elevation of the relief valve in the low pressureline for controlling the ventilation of the boiler and the feed of theoil to the boiler; and

Fig. 6 is a like view of the pressure regulator.

In the practice of the method of this invention forcontrolling thecombustion of oilin oil burners, the oil is caused to flow through anorifice of relatively large size such as to enable all matter ordinarily)resent in fuel oil to pass freely through it, and alow pressure drop ordifferential usually less than one pound per square inch, which isapm-oximate 1y equivalent to 30 inches of oil, is utilized to produceflow of oil through the orifice to the burner. The size of the orificein individual installations is preferably constant, and the control ofthe flow of oil to the burner is erfected by varying the pressuredifferential across the orifice between zero and an amount which formost installations does not exceed one pound per square inch. A gaseousfluid is, preferably, employed to produce the pressure drop across theorifice, and the oil is caused to flow through the orifice under a headcorresponding to the difference in gaseous fluid pressures on the oilsupply side of the orifice and on its delivery side. The gaseousfluidmay conveniently be used for atom- I ried out by apparatus of varyingforms.

izing the oil in the burner, and in such a case, the fluid is employedfor controlling the feed of oil to the burner at a pressure less thanthe atomizing pressure.

The ventilation of the burner is also controlled by the pressure of thegaseous fluid in such a manner that the amount of air supplied to theburner will always be sufficient for the complete combustion of the oilwithout substantial excess. The rate of feed of oil to the burner islimited to a desired maximum by limiting the pressure differentialacross the orifice. This is in turn effected by sul jeoting the deliveryside of the orifice .to at mospheric pressure and limiting the pressureof the gaseous fluid on the oil at the supply side of the orifice. Thegaseous fluid, preferably, controls the ventilation of the burner undera pressure substantially equal to the pressure imposed on the oil.Various kinds of gaseous fluids may be used without departing from theprinciples of the invention. In the application of the 111Vc11 tion tosteam boilers, however, the gaseous fluid pressure for regulating thefeed of the oil and the ventilation of the burner is, preferably,obtained through the agency of steam withdrawn from the boiler.Moreover, when the invention is used in connectionwith steam boilers,the feed of oil to the boiler furnace is reduced whenever the pressureof the steam in the boiler tends to exceed a predetermined degree. I V gThe apparatus shown in theaccompanying drawings constitutes a convenientand sati factory means wherebythemethod of this invention may be putintopractice. It is recognized, however, that the method may be c.-cordi-ngly, the apparatus herein disclosed is to be considered asillustrative only of means by which the method may be applied in acommercial way.

In the illustrated construction, a field boiler 10 of the type used'fordrilling oil wells is provided with a sub-furnace 12 in which is placedan oil burner 14. As shown, the oil burner 14 comprises a cylindricalchamber in which is fitted a core 16 having a single opening 18 for oiland a plurality of openings 20 below the opening 18 for conducting anatomiain fluid into close contact with the oil. The arrangement of theopenings 20 is such as to form the atomizing fluid into a fan-like layerupon which the oillfalls as it issues from the opening '18. The oilburner 14 does not require further description inasmuch as it is of atype well known to the trade and constitutes per se no part'of thepresent invention.

Oil is conducted to the burner 14 by a pipe 22 which communicates withthe burner sub stantially in line with the opening 18. The pipe 22extends through the front wall of the sub-furnace 12 and is connected atits outer a strainer to prevent the passage of large forelgn ob ects ofa kind not ordinarily present in fuel oil.

The flow-regulating devlce 26 comprlses a member 32 provided with anorlfice or re stricted opening 34, and means for creating a low drop inpressure across the orlfice tov cause oil to flow through it to theburner 14.

in the present exemplification of the invent on, the pressure of agaseous fluid is utilized to regulate the flow of oil through theorifice 34. Consequently, it is desirable, in

order to cause the rate of flow of oil through the orifice to beinfluenced by the least possible number of variable factors and therebyenable the rate of flow of the oil to be regulated with the greatestpossible accuracy, that the pressure on the oil as it enters theflow-controlling device 26 shall have no eff feet on the pressure at theorifice 34. Manifestly, if oil is supplied to the device 26 by a pump,the pressure on the oil as it enters thedevice will vary with the speedof the pump and the head of oil in the pipe 28, and

if oil is supplied to the device 26 by gravity alone, the pressure onthe oil will still vary in accordance with the level ofthe oil in theultimate source of supply. To the end that the rate of flow of oilthrough the orifice 34 may be entirely unafii'ected by the pressure ofthe oil asit enters the device 26,

the flow-controlling device includes a trap or chamber 36 located on thesupply side of the orifice 34 and provided with means for maintainingthe oil in the trap at a fixed level. As shown, such means comprises avalve 38 (Fig. 3) arranged to control the inflow of oil to the chamber36 from the pipe 28 and. connected by suitable linkage 40 to a float 42.The arrangement of these parts is such that when the oil tends to riseabove the fixed level, the float 42is raised and moves the valve 38toward closed position, whereas when the oil tends to recede below thefixed level, the float 42 falls andmoves the valve 38 toward openposition.

The trap 36is formed at one side near its bottom with a projectingportion '44 in which i pipe 46 and on its delivery side with the orificechamber 48. As shown, the orifice memher is in the form of a platethreaded into the orifice chamber48 adjacent to the pipe 1 46, andtheorifice 34 is of the type commonly called an orifice, in thin plate.It is eviis of a type such that the introduction of an atomizing fluidinto it produces no suction in the oil pipes 22 and 24. In order toinsure against the creation of any suction 1n the pipes 22 and 24 andthe orifice chamber 48,

the chamber is is formed at its sides with two large openings 52. Theopenings 52 are preferably threaded to allow them to be closed by screwplugs 53 when necessary to prevent the entrance of dust into the chamber48.

Inasmuch as the orifice chamber 48 is open to the atmosphere, thepressure on the deliveryside of the orifice is substantially constant.Consequently, the rate of flow of oil through the orifice 34 may becont-rolled by gaseous fluid pressure imposed on the oil in the trap 36.In order to enable a low pressure drop to be readily obtained across theorifice 34 and to enable the pressure drop to be readilyreducedsubstantially to zero thus substantially suspending the flow ofoil to the burner 14. the oil in the trap 36 is preferably maintained atthe level of the orifice 34. With this construction, oil is caused toflow through the orifice only when there is a greater gaseous fluidpressure on the oil in the trap 36 than on the delivery side of theorifice 34, or, in other words, only when the pressure of the gaseousfluid in the trap 36 is greater than atmospheric pressure. Consequently,if the gaseous fluid pressure in the trap 36 is reduced to atmospheric,the flow of oil to the burner 14 through the orifice 34 is discontinued.

The use of a low pressure drop for producing flow of oil through theorifice 34 is of particular importance in field boilers since it enablesoil to be fed to a boiler from a field tank by gravity. The pipe 28 ofthe illustrated installation is designed to receive oil from a fieldtank without the use of a pump. The expense and trouble which areavoided in this way are very considerable.

Means is preferably provided for enabling a small quantity of oil to besupplied to the burner 14 at any time regardless of pressure conditionsin the trap 36. A convenient embodiment of such means consists of apilot pipe 54 interposed between the oil trap 36 and the pipe 22 andprovided with a valve 55.

In the illustrated construction, the gaseous fluid which controls thefeed of the oil is conducted to the trap 36 from a stand-pipe 56connected to the top of the trap by a pipe 58 (Fig. 2). A second pipe 60leads from the trap 36 below the oil level to the stand-pipe 56. Withthis construction, it is evident that the oil level in the stand-pipe 56will be the same as that in the trap 36. In order to en able the oillevel to be observed by the operator, a gauge glass 62 is connected tothe stand-pipe above and below the oil level by pipes 64 and 66respectively. A second gauge glass 68 communicates at its lower end withthe'stand-pipe 56 below the oil level and is open to the atmosphere atits upper end The stand-pipe 56 may also be provided at its bottom witha pet-cock 70.

Since the gauge glass 68 and the orifice chamber 48 are both open to theatmosphere, the height of oil in the glass 68 indicates the pressuredifferential or drop across the orifice 34. The glass 68 is calibratedso as to enable the pressure differential to be measured. In order tomeasure the rate of flow of oil directly, the gauge glass. 68 must becalibrated to correspond with the size of the orifice 34. If, for anyreason, the size of the orifice should be changed, a new gaugeglass 68would have to be substituted for the one previously in use. If the gaugeglass 68 is calibrated to indicate the pressure differential only, therate of flow of oil in any installation can be readily computed from theindicated differential and the known size of the orifice 34.

In actual installations which have been operated very successfully, anorifice 34 of onequarter inch diameter and a pressure drop across theorifice of .65 pounds of oil have been employed in firing a 250 horsepower boiler at 125% of its rated capacity. In these installations thefuel oil used was Kansas crude having a specific gravity of about 34Baum. The size of the orifice 34 is decreased in firing boilers ofsmaller capacity, but by using a low pressure differential, the size ofthe orifice for boilers of all capacities may be made large enough topermit all foreign solid matter usually present in fuel oil to passfreely through it. In this connection it is to be noted that oilsordinarily used commercially for fuel purposes contain a considerableamount of solid matter which it is impractical to remove from the oil byfiltration or otherwise. Such matter usually consists of partieles ofdirt, etc. If the strainer 30 were, designed to remove such particlesfrom the oil, it would be quickly clogged by a large accumulation ofmatter. For this reason the strainer 30 is designed to remove from. theoil only objects of considerable size. Such objects are not usuallypresent in fuel oil, and the strainer may therefore be used for a longtime without cleaning.

Theaccuracy with which the rate of feed of oil to a burner can becontrolled and regulated depends in great measure on the number ofvariable factors afiecting the feed of the oil. In the use of thisinvention, the number of such variable factors is reduced to a .minimum.The size of the orifice 84 cannot be changed Without substitution of oneplate .32 foranother. Such a substitution is generally not made after aninstallation is complete and cannot be made without interrupting theoperation of the burner. Moreover, when one orifice plate is substitutedfor another, the substitution is not effected as a temporary adjustmentbut with a view topermanency, as, for example, when the capacity of theburner is changedk The status of the orifice 34 as a fixed rather than avariable factor in controlling the rate of flow of oil to the burner isfurther established by the fact that the orifice is always made ofsufficient size so that it will interpose no obstruction to the passagethrough it of foreign solid matter suchas isordinarily present in fueloil. Thisprevents solid matter from restricting either temporarily orpermanently the actual size of the opening available for the passage ofoil. As already indicated the 5 rate of flow of oil througlilthe orificeis entirelyuninfluenced bychange in the pressure on the oil in the pipe28. The creation of a pressure drop across the orifice 34 involves twofactors one of which, namely, thepressure on the delivery side of theorifice is substantially constant. Consequently, the only variablefactor afiecting the rate of flow of oil to the burner 14 is thepressure of thegaseous fluid on the oil inthe trap 36. This inventionnot only enables the rate of flow of oil to the burner 14 to becontrolled and regulated with great accuracy, but it also enables therate of flow of oil to be very accurately determined by reference to thegauge glass 68.

Where a gaseous fluid under a pressure either greater or less thanatmospheric pressure is conveniently availableflt is preferred toutilize such fluid at one'side of the orifice and atmospheric pressureon the other side of the orifice for producing and regulating the flowof oil through the orifice. It is recognized, however, that certain ofthe principles of the invention involving the use of alarge orifice anda low-pressure drop across the orifice, can be applied in a commercialway with other means forinducing adrop in pressure across the orifice.For example, varying gaseous fluid pressures may beem'ployed on bothsides of the orifice, and'when a gaseous fluid is not readilyavailablethe dropin pressure across the orifice maybe varied by-vary ingthe head of the liquid oil. on the orifice.

In the latter event, however, the pressure of the oil at theorifice-should be so controlled as to be'independent of the pressure atwhich the oil is supplied to the flow-controlling mechanism.

The pressure of the gaseous fluid in the trap 36 may be varied manuallyor automatically within the scope of theinvention. In the illustratedconstruction, a mixture of steam and air is employed as thegaseous fluidand the pressure of the gaseous fluid is controlled automatically. Tothis end, steam is withdrawn from the boiler 10 by a conduit including apet-cock 72, valve 74, strainer 76,,

pressure regulator 78, pressure gauge 80, orifice nipple 82, andblow-cock 84. The steam isreduced to a pre-determined pressure by thepressure regulator 78, and its pressure is further reduced by passingthrough the orifice nipple 82. The conduit 7 0 communicates on theoutlet side of the nipgauge glass 68 may be mounted on the trap Thepressure regulator 78 isset to -reduce the steam to the pressure bestadapted for atomizing the oil in theburner 14, and a coni necting pipe88 leads from the conduit 70 intermediate between the pressure regulator78 and the orifice nipple 82 to the burner. The

pressure regulator 7 8 is of known construction and does not requiredetailed description. As seen in Fig. 6, steam passes through theregulator from left to right and is governed by a valve90. The valve isconnected to a diaphragm 92, the under side of which is subjected to thepressure of the steam on the outlet side of the valve. If the pressureof the steam on the outlet side of the regulator tends to exceed thatfor which the regulator is set, the diaphragm 92 is forced upwardlyagainst the, tension of a spring 94 thus causing the valve 90 to movetoward closed position. If, on the other hand, the pressure of the steamtends to fall below that for which the-regulator is set, the spring 94moves thevalve 90 toward open position.

As hereinbefore indicated one of the features of the inventioncontemplates that the rateof flow of oilto the burner v 14 shall bereduced whenever the pressure of the steam boilein Asshown, the device96 is located at one end of the low pressure line 86 and comprises acasing formed to provide an inlet chamber 98 and an outlet chamber 100,

trolled by the pressure ofthe steam in the the latter being open to theatmosphere. The I flow of fluid through the device96 is normallyprevented by a valve 102 maintained in closed position by a lever 104and weight 106. The device 96 is formed at its upper end witha chamber108 containing a dia phragm 110 connected to the valve 102. The chamber108 above the diaphragm 110 is closed to the admission of air and hasconnected to it a pipe 112 leading from the conduit 7 on the inlet sideof the pressure regulator 78. The pipe 112 conducts steam to the chamber108 of the pressure relief device 96 substantially at boiler pressure.Consequently, if the pressure of the steam in the boiler tends to exceedthat for which the device 96 is set, the valve 102 of the device isopened, thus relieving the pressure in the low pressure line 86 andreducing the feed of oil to the boiler.

The rate of supply of air for supporting the combustion of the oil fedto the boiler is controlled by a damper 118 in the stack or flue 120 ofthe boiler in such a manner that whatever the rate of feed of oil to theboiler may be, air is admitted to the boiler in sufficient quantity tosupport the combustion of the oil but without any considerable excess.As shown, the damper 118 is fixed on a rotatable shaft 122, provided atone end with a pulley 124 over which passes a cable. 126. The cable 126is attached at one end to a small weight 128 and at its other end to anactuator arranged to move vertically in accordance with the pressure inthe low pressure line 86.

The actuator may have various forms. In

the illustrated construction, however, it is in the form of an invertedbell 130 closed at its 8 upper end and having its open lower end im suchthat when the damper is closed, the bell 130 isin its lowermostposition, and the crank arm 136 extends horizontally from the shaft 122in a direction such as to cause the weight 138 to swing downwardly asthe bell 130 is raised. From the foregoing it will be understoodthat theweight 138 tends in the closed position of-the damper to raise the bell130. As the bell 130 is raised the moment of the weight 138 tending tolift the bell gradually decreases so that the gas pressure necessary tofurther elevate the bell increases as the bell attains the higherpositions of its movement. 7

By reference to the well known equation for determining the rate of flowof liquid through an orifice, Q=c adm, in which Q represents thequantity or rateof flow, a,

the area of the orifice, g, the gravity co-efiicient, h, the pressuredrop across the orifice and c, a co-efiicient based on the shape of theorifice, it will be understood that the rate of flow of oil through theorifice 34 varies in accordance with the square root of the pressure inthe low pressure line 86.

For convenience in explaining the principle of operation of the damper118, the factors affecting the action of the damper may be symbolized asfollows:

VV=the mass of the weight 138,

X=the net weight of the bell 130, that is, the weight of the bell minusthe weight of the striker 142 and weight 128;

R=the moment arm of the bell 130 and Weight 136 in inches;

a=the transverse area of the bell in square inches; v

P=the gas pressure in the bell in inches of water;

A=the transverse area of the stack 120 at the damper;

D the area of the damper; and

=the angle made by the arm 136 and the damper 118 with the horizontalplane through the damper axis.

The moments of the weight 138 and the bell 130 when the arm 136 is inhorizontal position and the damper 118 closed are usually madesubstantially equal so that when there is'atmospheric pressure only inthe bell 130, the weight 138, damper 118, and bell 130 are inequilibrium. Accordingly W It=X R, and when the length of the arm 136equals the radius of the wheel124e, W and X are also made substantiallyequal.

One cubic inch of water weighs .036127 lbs. Accordingly, for anyposition of the damper 118 between wide open and closed positions,

WR Cos =XR .036127 aPRor X036127 a P W mentioned equation the area ofthe damper opening is-ascertained to be equal to Experiments appear toindicate that the rate of flow of airthrough the boiler 10 variessubstantially in direct proportion to the area of the opening defined bythe stack damper, and that the amount of air supplied to the furnaceswill be properly proportioned to the rate of feed of the oil, when thearea of the damper opening varies in about the same ratio as the rate offeed of oil to the boiler furnace.

When the damper 118 is moved from closed position a comparatively largeangular movement of the damperproducesu only a small increase in area,of thedamper opening. Consequently, if the damper 118 were caused tomove angularly in direct proportion to the pressure in the bell 180, theboiler would be properly ventilated only when the pressure in the bell130 approximated themaximum pressure required to cause the damper 118 tobe fully opened. At all lower pressures the boiler would be badlyunder-ventilated. By causing the area of the damper opening to vary inproportion to-the pressure in the bell 130, the rate offiow of airthrough the boiler furnace is caused to vary in a ratio which quiteclosely approximates the variations in the rate of flow of oil to theburner 14:.

It is never desirable that a stack damper be made to fit a stack tightlybecause of the danger of the accumulation of explosive gases. In the useof thisinvention the existence of a considerableareaof leakage betweenthedamper 118 when in closed position and i the stack causes the ratiosof the ventilation and the rate of flow of oil to approach each othermore closely than if there Were no leakage, If the leakage area aboutthe damper 118 when in closed position is 25% of the transverse area ofthe stack ,at the damper,

and the installation is set to attain maximum combustion capacity at-apressure of 18 inches of water, the ventilation ,of the boiler would betheoretically correct at 33% of combustion capacity and a pressure of 2inches under such conditions is actually; slightly f over-ventilated,due it is thought, tothe effect of increasing flue-gas temperature withincreased rates of combustion andalso to the fact that the law of flowof gases past the stack damper is not exactly the same as the lawgoverning flow of fluids through an orifice in thin plate)? r i Ithas-been determined in a number ofcommercial installations that by theuse. of this invention, the ventilation of a burnermay be accuratelyproportioned to the rate of feed of oil to the burner, as evidenced by aconstant percentage of CO in the exhaust gases, between combustion ratesof and 100%. I It is not ordinarily of commercial importance to regulatethe ventilation of a burner in strict accordance with the rate of flowof oil to the burner at rates of combustion less than 25%; of maximum.

In actual practice the weight138 and the degree of opening of the damper118 may be made greater or less according as the draft, intensity whichgoverns the velocity of flow of gases through. the stack is smallor-large. This adjustment to compensate for varying draft intensities ismade possible by the fact that the area of the damper opening isautomatically kept in direct proportion to the pressure in the bell 130irrespective of the weight of the parts 138 and 130. It is contemplated,however, that, inthe use of the invention, the draft intensity will alsobe regulated in the usual manner as, for example,by secondary dampers oropenings at the inlet to the boiler furnace. g

If the boiler 10 were operated at a heavy load it would be possible foroil to be fed to the burner 14 in'excess of the safe combus tioncapacity of the boiler without generating sufficient pressure in theboiler to operate the relief device 96. It is desirable that the rate offlow of oil to the burner shall be limited to the safe-combustioncapacity of the boiler regardless of thelo'ad on theboiler. To this endthe low pressure line 86 is provided with an upstanding portion 139which is open to theatmosphere. The flow of fluid through the portion139 is controlled by a butterfly valve 140 whichis normally closed, butis arranged to be opened Whenever the pressure in the low pressure line86 tends to exceed a pre-deter-mined maximum. Manifestly, since the rateof flow of. the oil depends on the pressure in the line 86, the reliefof such' pressure at a pre-determined mamimum de gree limits the rate offlow of oil to the boiler furnace.

In order to relieve the pressure in the low pressure line 86 when therate of feed of the oil tends to exceedthe maximum rate desired, thevalve 140 in theupstanding portion 139 of the pressure line 86 isoperatively connected to a lever 141 having an opening in one endthrough which the cable 126 passes. The. cable 126 carries a Weight orstriker 142 positioned so asto engage the end of the lever 141 andthereby open the valve 140 when the damper 118 attains the most widelyopened position for which it is adjusted. The striker 142 may be locatedin various positions on the cable 126 in accordance as the maximumdegree of opening of the damper 118 is changed. The valve 140 isreturned to closed position by a weighted plunger 144 connected to theother end of the lever 141. The plunger 144 is preferably enclosed in adash-pot so as to dampen the movements 01 the valve 140. The weight 128is of a size sufficient only to properly control the cable 126 andstriker 142.

The flow of steam through the nipple 82 induces flow of air into the lowpressure line 86 through the aspirator 84. The air'reduces the amount ofsteam required to be supplied to the line '86 not only directly bytaking the place of steam that would otherwise be required to producethe necessary pressure but also indirectly by reducing condensation ofthe steam in the low pressure line 86, oil trap 36, and bell 130. Thereduction in the condensation of the steam arises from the fact that amixture of steam and air has a much lower temperature than pure steam atthe same pressure.

The low pressure line 86 is preferably pro vided at its low point with apet-cock 146 (Fig. 2) which is left open continuously to allow theescape of water formed by condensation of steam in the line. The amountof steam and air which issues from the petcock is negligible. Thepet-cock 72 may be opened to permit the escape of water from p the highpressure conduit 70.

It is first decided what the maximum gaseous fluid pressure on the oilin the trap 36 shall be. Then the mass of the weight 138 and the netweight of the bell 130 are calculated from the equation COS wer??? @P Inthis computation X andW are assumed to be equal and they are socalculated as to cause the damper to be opened at an angle of 7 or 80degrees to the horizontal at the maximum burner pressure. Thecross-sectional area of the bell, denoted by a, in commercialinstallations is about 60 square inches.

Although in the above calculations the weights X and W have been assumedto be.

feet of making the weight X greater than the weight l/V is to cause theopening of the damper to be delayed with respect to the development ofpressure in the oil trap 36 and the low pressure line 86 and to causethe damper to close a short time before the pressure in the bell 180 isreduced to atmospheric. The weight of the bell 130 is sufficiently closeto the weight 138 to enable the weights X and 1V to be calculated fromthe above equation with sufi'icient accuracy to satisfy all practicalrequirements.

In the use of the illustrated apparatus, assuming the boiler to be cold,the valve in, the pilot pipe 54 is first opened to allow oil to flow tothe burner 14. When steam has been generated in the boiler, the valve.55 is nearly or fully closed, and the valve 74 in the conduit is openedto allow steam to pass into the low pressure line 86. The pressureregulator 78 is set to cause steam to be delivered from it at a desiredpressure which is indicated by the gauge 80. The pressure of the steamis further reduced by the orifice nipple 82 and air is admitted throughthe asp'irator 84 to form a mixture of steam and air. Steam at thepressure determined by the pressure regulator 78 is conducted to theburner 14 to atomize the oil, and the size of the orifice in the nipple82 is so proportioned to the pressure of the steam as it issues from theregulator 7 8 that the mixture of steam and air in the low pressure pipe86 may develop a pressure greater than that necessary to cause oil to befed at the maximum rate. The pressure which maybe developed in the lowpressure pipe 86 is, however, limited by the size of the orifice in thenipple 82 to a degree such that it may quickly be reduced to therequired extent in the event that the steam pressure in the boiler tendsto become excessive or the pressure in the low pressure line 86 tends toexceed that necessary to cause oil to be fed to the. burner at thedesired maximum rate. The valve 102 of the pressure relief device 96 isoperated to reduce the pressure in the low pressure line quickly in casethe pressure of the steam in the boiler tends to exceed the degreedetermined by the relief device. The striker 142 on the cable 126, is,however, generally moved very slowly in response to like movements ofthe bell 130. Consequently, the

valve 140 is not moved abruptly but is gently urged toward open positionby the weight of the striker resting on the lever 141. The plunger 144,and the dash-pot also tends to impart a gentle action to the valve 140.The result of the above described action of the valve 140 is to causethe conditions which control the operation of the boiler to bemaintained substantially constant when the boiler is being operated ator near'the full capacity of the burner 14.

The operation of the boiler may be quickly discontinued by closingeither the valve 74 the high pressure conduit 70 or the valve "29. inthe oil supply pipe 28 or both. When the operation of the boiler isstopped by closing the valve 745, the pressure ofthe steamv and air. inthe low pressure line 86 and oil trap, 36 is quickly relieved by theemission of steam and air through the aspirator 84. Inasmuch as thepressure in the line 86 is always very small, the relief of thepressurewhen V the valve 74 is closed is practically instantaneous. In case theoperation of a field boiler a burner in the furnace comprising an oilcontaining chamber, a' member on the delivery side of the chamberprovided with an orifice through which theoil is fed, means formaintaining the outlet side of the orifice under atmosphericpressure,:means for producing a superatmospheric pressure in sa1d oilchamber to feed Oll through the orifice, means for maintamlng'the oil inthe 011 chamber constantly at the level of the ori- V fice, and a directgravity run between said orifice and said burner. I i 2.- Inan apparatusof the class described, a

boiler, an oil burner for heating said boiler,

and means for feeding oil to said burner comprising a supply chamber,connectlons bee tween said chamber and said burner including arestricted opening of uniform area, connections between said boiler andsaid chamber including a reducing valve, a restricted opening ofconstant area intermediate said reducing valve and said chamber, andmeans for automatically ventingthe pressure in said secondmentionedconnection and chamber.

3. In an apparatus of the class described,

a field boiler, afurnace for the boiler provided with a burner, andmeansfor feeding oil to the burner comprising a member provided withanorifice through which the oil is fed, an oil containing chamber on thesupply side of the orifice, means for maintaining the oil in the chambersubstantially at the level of the orifice, means for subjectingthedelivery side of the orifice to atmospheric pressure, and means forimposing a gaseous fluid pressure slightly greater than atmospheric onthe oil in said chamber to produce flow of oil through the orifice, saidorifice being of sufficiently large size so as to enable an adequatesupply of fuel oil to be delivered to said boiler with a gaseous fluidpressure in said chamber of 30 inches of oilso that oil may be fed bygravity from a field tank to the chamber.

4. Inan apparatus of the class described, an oil burner, and means forfeeding oil to the burner comprising an oil trap, a hollow vmemberassociated with the trap, an orifice plate arranged to communicate onits supply side with the hollow member, a chamber communicating withsaid plate on its delivery side, means for exerting pressure notsubstantially exceeding one poundper square" inch on the oilin the trap,and meansfor conducting oil under atmospheric pressure from the deliverysideof the orifice to the burner;

i '5. In an apparatus of the class described," an oil burner, and meansfor feeding oil to the burner comprisingan oil trap, means formamtalning the oil in the trap at a predetermined level, a pipecommunicating with the trap below the level of the liquid in the trapand extending upwardly, a chamber en-v closingjthe upper end of the pipeandopen v to the atmosphere, an orifice plate mounted in substantiallythe same horizontal plane as the level of liquid in the trap andarranged to communicate .on its supply side with the plpe and on itsdelivery sidewith the chamber, means for conducting oil by gravity fromthe delivery side of the orifice to the burner, and means for imposinggaseous" pressure greater than atmospheric on the 011m the trap toproduce flow of oil to the burner.

6. 'Inan apparatus of the class described,

aboiler, means for feeding oil to the furnace of saidboiler, mechanismfor controlling the V ventilationof the furnace, a fluid pressure linefor controllingfthe feed of the oil to the furnace and for operatingsaid mechanism,

means for conducting steam from the boiler tofthe fluid pressure 11118,and a pressure regulator and a constant area orifice member forcontrolling the passage of steam from the boiler to the pressure line. Y

' 7, In an apparatus of the class described,

a boiler, means for feeding oil to the furnace of saldboller, mechamsmfor controlling the iventilation of the furnace, a fluid pressure linefor controlling the feed of oil to the furnace and for operating saidmechanism, a

pipe for. conducting steam from the boiler to the pressure line, and .anaspirator in said pipe for causing air to be drawn into the pipe inorder to dllute the steam and thus reduce condensation of steam in thefeeding means and in said mechanism. 7 V a j 8. In an apparatus of theclass described, a

boiler, means for feedingoilto the furnace of-said boiler comprising amember provided 7 with an orifice, a conduit for conducting l steam fromthe boiler tothe feeding means on the supply side of the orifice so astoimpose greater pressure on the oil at the supply sideof the orifice thanon the delivery side [said aspirator being constructed to cause air 'tobe drawn into said conduit by flow of steam through the conduit when thevalve is open and to permit flow of air and steam outwardly from theconduit when the valve is closed so as quickly to reduce the pressure inthe feeding means to atmospheric.

9. In anapparatus of the class described,

.a boiler, means for feeding oil to the furnace of said boiler, echanismfor controlling the ventilation of the furnace, a lineof piping forconducting steam from the boiler, a pressure regulator in said piping,an orifice member on the outlet side of the regulator, a connectionbetween the piping and the furnace for conducting steam to the furnaceto atomize the oil, said connection communicating with the pipingbetween the pressure regulator and the orifice member, and meansconnected with the piping on the outlet side of the orifice member fortransmitting steam at ,low pressure to the feeding means andsaidmechanism.

10. In an apparatus of the class described,

a boiler, means for feeding oil to the furnace of said boiler, a line ofpiping for conducting steam fronithe boiler, a pressure regulator insaid piping, an orifice member on the outlet side of the regulator, aconnection between the piping and the furnacefor conducting steam to thefurnaceto atomize the oil, said connection communicatingwith the pipingbetween the pressure regulatorand the orifice member, and a connectionbetweenthe piping on the outlet side of theorifice member and thefeeding means for transmitting I steam at low pressure to the feedingmeans.-

11. The method of controlling combustion in oil-fired boilerfurnaceswhich consists in withdrawing steam from the boiler, reducingthe steam to a pre-determined pressure, uti-' lizing steam at suchpressure for atomizing the oil in the boiler furnace, reducing the steamto a still lower pressure, andutilizing steam at the last-mentionedpressure for controlling the feed of oil to the'furnace.

12. The method of controlling combustion in a furnace for which oilisatomized by a fluid which consists in supplying the atomizin g fluidat a constant pressure, and utilizing a portion of the atomizing fluidat a varying pressure lower than the atomizing pressure for controllingthe feed of oil to the burner.

13. The method of controlling combustion in oil-fired boiler furnaceswhich-consists in withdrawing steam, from the boiler, reducing the steamto a 'pre-determmed pressure,

utilizing the steam at such pressure for atomizing the oil in thefurnace, further reducing the pressure of the steam, and utilizing thesteam at the last-mentioned pressure for controlling the ventilation ofthe furnace.

14c. The method of controlling combustion in oil-fired boilers whichconsists in withdrawing steam from the boiler, reducing the steam to apre-determined pressure, utilizing steam at such pressure for atomizingthe oil, further reducing the pressure of the steam, utilizing the steamat the last-mentioned pressure for controlling the ventilation of theboiler and the feed of the oil, and utilizdrawing steam from the boiler,reducing the steam to a predetermined low pressure which remainssubstantially constant regardless of changes in pressure of the steam inthe boiler, utilizing a stilllower fluid pressure derived from saidconstant pressure for controlling "feed of oil to the boiler furnace,and releasi the oil feed control pressure whenever the pressure of thesteam in the boiler tends to increase beyond a predetermined amount.

16. A method of controlling combustion in boiler furnaces comprisingestablishing a stream of elastic fluid flowing continuously duringperiods of normal steam pressure in the boiler to be controlled,developing a rela tively low super-atmospheric pressure by means of saidstream and utilizing such pressure to control the flow of fuel to theboiler furnace, and governing the rate of flow of fuel to the furnace bygradually opening said stream to the atmosphere to a greater or lessextent in accordance with Variations of the steam pressure of theboiler.

17. In an apparatus of the class described, a boiler, pressurecontrolled means for feeding oil to the furnace of the boiler, means forconducting steam from the. boiler to the feeding means and separatemeans for relieving:

pressure of the steam in the boiler tends to exceed a predeterminedamount. i

In testimony whereof I aflix my signature.

BENJAMIN GREENFIELD.

